Method of fabricating a housing assembly

ABSTRACT

An axle assembly includes an upper and lower housing joined to form a chamber for a differential gear assembly. The upper and lower housings are fabricated by a method including the steps of forming the upper housing from a first sheet of material and forming the lower housing from a second sheet of material. The upper housing includes an opening for the differential gear assembly and the lower housing includes a bowl portion disposed opposite the opening. The upper and lower housings are joined by a weld to from the axle housing. The lower housing includes leg portions that form a single unified structure with the bowl portion to improve structural rigidity and simplify assembly.

BACKGROUND OF THE INVENTION

[0001] This invention generally relates to a method of fabricating an axle housing assembly, and specifically to a method of fabricating an axle housing having a lower housing defining a bowl portion enclosing a differential gear assembly.

[0002] Conventional axle housings are fabricated utilizing various processes including casting, forging and stamping. Stamping processes have several advantages over other known processes such as cost efficiencies, strength and adaptability to various desired configurations. Conventional fabrication processes for stamped axle housings begin with a specially sized and shaped blank of steel. The blank size and shape corresponds with progressive stamping dies that shape and form the blank into a completed section of the housing.

[0003] Typically, axle housings fabricated from a stamping process include first and second housing halves fabricated separately and joined by welding. The first and second housing halves form leg sections extending from a differential mounting section. Axle shafts are supported within each leg section and are connected to a differential gear assembly mounted within the mounting section. The mounting section is formed by the joined first and second housing halves to form upper and lower halves of a substantially circular opening. The differential gear assembly is mounted to the housing assembly such that a gear extends into the opening to engage the axle shafts.

[0004] The gear is of a larger diameter than is capable of being completely enclosed within the two joined housing halves. A cover attached to the housing at the mounting section covers the portion of the gear extending from the axle housing. The cover is a separate piece attached to the housing assembly. As appreciated, additional parts contribute to additional cost, and require additional assembly steps. Further, the joint between the cover and the axle housing creates an additional potential leak path for lubricant contained within the axle housing.

[0005] Accordingly, it is desirable to develop an axle housing assembly and method of fabricating an axle housing that, reduces the costs and the number of assembly operations.

SUMMARY OF INVENTION

[0006] An embodiment of this invention is a method of fabricating an axle housing assembly including the steps of forming an upper housing from a first sheet of material and a lower housing including a bowl portion from a second sheet of material.

[0007] The upper housing includes an upper mount section having an opening to receive a differential gear assembly. The lower housing includes a lower mount section including a bowl portion. The lower housing includes first and second leg portions extending from the lower mount section. The bowl portion and first and second leg portions form a single unified part. The upper and lower housings are joined along a seam by a weld to form a complete housing defining a gear assembly chamber. The lower housing is a single unified part having a bowl portion disposed opposite the opening within the upper housing. The bowl portion increases rigidity of the lower housing that in turn strengthens the entire housing assembly. The structural rigidity of the unified lower housing is increased because the bowl portion is thicker and includes a slightly elongated spherical shape. Further, the unified configuration of the lower housing eliminates additional parts and joints. The elimination of unnecessary joints reduces potential leak paths and increases structural rigidity.

[0008] Accordingly, the axle housing assembly fabricated according to this invention includes a single unified lower housing section including the bowl portion enclosing the differential gear assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:

[0010]FIG. 1 is a perspective view of an axle housing assembly with a differential gear assembly;

[0011]FIG. 2 is a perspective view of the axle housing assembly without the differential gear assembly;

[0012]FIG. 3 is a perspective view of a lower housing;

[0013]FIG. 4 is a perspective view of an upper housing;

[0014]FIG. 5 is a perspective view of a differential gear assembly;

[0015]FIG. 6 is partial sectional view of the axle housing assembly;

[0016]FIG. 7 is a cross-sectional view of the housing assembly with the installed differential gear assembly; and

[0017]FIG. 8 is a schematic representation of fabrication of an axle housing according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] Referring to FIGS. 1 and 2, an axle housing assembly 10 includes an upper housing 12 and a lower housing 14. The upper housing 12 includes an opening 22, best shown in FIG. 4, and is formed from a single sheet of material. The lower housing 14 is joined to the upper housing 12 and is formed from a second sheet of material. The lower housing 14 includes a bowl portion 24 disposed opposite the opening 22. A differential gear assembly 42, shown schematically, mounts to the upper housing 12 and includes a gear 44 (FIG. 6) extending through the opening 22 and into the bowl portion 24.

[0019] Although upper and lower housings 12, 14 are shown and described, the specific orientation of each part of the housing assembly 10 can vary according to specific application requirements. Furthermore, although a top mounted gear assembly 42 is shown, it should be understood that it is within the contemplation of this invention to construct housing assemblies for face or side mounted gear assemblies.

[0020] The housing assembly 10 includes a mount portion 16 for the differential gear assembly 42. The mount portion 16 may be an expanded area located at or adjacent a central point within the axle housing assembly 10. There are several configurations of axle housing assemblies 10 commonly know to those skilled in the art that vary relative to the position of the mount portion 16. First and second leg portions 26,28 extend from either side of the mount portion 16 to form elongated chambers for axle shafts driven by the differential gear assembly 42. The mount portion 16 may be centrally located such that the first and second leg portions 26,28 are of equal length or as shown adjacent the mount portion 16 such that the second leg portion 28 is longer than the first leg portion 26.

[0021] The first and second leg portions 26, 28 terminate at first and second ends 38, 39 respectively. The first and second ends 38,39 of each housing 12, 14 include a generally C-shaped cross-section 36 (FIGS. 3 and 4) that are joined to form substantially circular ends. A wheel mount assembly 40 is mounted to the first and second ends 38, 39. The wheel mount assemblies 40 are of any known configuration.

[0022] The upper and lower housing 12,14 are joined along a welded seam 46 extending along the entire length of the axle housing assembly 10. The upper and lower housings 12, 14 are welded along the seam 46 to provide a structurally rigid axle housing assembly 10. The specific welding process is as known. Further, the seam 46 is configured according to known techniques to accommodate application specific requirements for durability, strength and rigidity.

[0023] Referring to FIGS. 3-5, the upper housing 12 is formed from a first single sheet of material or a blank. The sheet of material is of a shape corresponding with subsequent stamping operations to form the final desired shape of the upper housing 12. From the original sheet of material, the configuration of the upper housing 12 is stamped utilizing known processes. The upper housing 12 includes an upper mount section indicated at 18 to differentiate it from the assembled mount section indicated at 16 in FIGS. 1 and 2. The upper mount section 18 includes the opening 22 into which the differential gear assembly 42 is installed. The upper mount section 18 is generally circular and accommodates installation of the differential gear assembly 42. The upper housing 12 is a single unified piece that includes an upper half of the first and second leg portions 26, 28.

[0024] The lower housing 14 is stamped from a second single sheet or blank. The original sheet of material is of a size and configuration that corresponds to subsequent stamping operations to progressively form the completed lower housing 14. The lower housing 14 includes a lower mount section indicated at 20 to differentiate from the assembled mount portion indicated at 16. The bowl portion 24 is disposed within the lower mount section 20. The bowl portion 24 is part of the single unified lower housing 14. The lower housing 14 includes a lower portion of the first and second leg portions 26, 28. The unified construction of the lower housing 14 eliminates the need for a separate cover to enclose the differential gear assembly 42 within the completed housing assembly 10.

[0025] Further, the bowl portion 24 of the lower housing 14 strengthens the overall structure of the completed housing assembly 10 by eliminating the joint required by a separate cover attached to the lower housing 14. In addition to the increased rigidity provided by the unified construction of the lower housing 14, the reduction of seams and joints eliminates potential leakage paths from the completed axle housing assembly 10.

[0026] Referring to FIGS. 6 and 7, the unified bowl portion 24 provides the additional required clearance for the gear 44 of the differential gear assembly 42. The lower housing 12 includes a surface 32 that defines a plane 34 extending through the bowl portion 24. The surface 32 is continuous through the mount portion 16 to distal ends of the first and second leg portions 26 and 28 that extend toward the wheel assemblies 40 attached to the first and second ends 38, 39. The surface 32 smoothly transitions in from the more planer surfaces at the leg portions 26, 28 through the bowl portion 24. The transition from the surface 32 into the bowl portion 24 is continuous and does not include seams or other surface interruptions.

[0027] The upper and lower housings 12,14 form a chamber 48 into which the gear 44 extends. The bowl portion 24 extends the chamber 48 beyond the plane 34 defined by surfaces 32 such that the gear 44 is enclosed within the upper and lower housings 12,14. The chamber 48 for the gear 44 is formed by the upper and lower housings 12, 14 without additional sections or parts. The gear 44 is enclosed within the axle housing 10 once mounted to the upper housing 12.

[0028] The bowl portion 24 is preferably spherically shaped and transitions from the planar surface 32 to a full depth of the chamber 48 accommodating gear 42. The spherical shape of the bowl portion 24 may also be elongated to reduce stress on the housing assembly 10. FIG. 7 illustrates the slightly elongated configuration of the bowl portion 24. As appreciated, the depth and configuration of the bowl portion 24 and the corresponding chamber 48 is specifically configured to accommodate the specific differential gear assembly 42 required for a specific application. The single unified structure of the lower housing 14, including the lower bowl 24, decreases the number of parts required to complete the axle housing assembly 10 and the number of operations required for assembly.

[0029] Referring to FIG. 8, a method of fabricating the axle housing assembly 10 is schematically shown and includes the initial step of providing a first sheet of material 50 configured and sized to produce the upper housing 12. The configuration of the first sheet of material 50 or blank corresponds with the specific stamping process utilized and the overall final desired configuration of the upper housing 12. A second sheet of material 52 is configured to correspond with stamping operations required to form the lower housing 14. A worker skilled in the art would understand the configuration required for the first and second sheets of material 50,52 to accomplish the desired final configuration of the upper and lower housings 12, 14. Preferably, the material comprising the first and second sheets of material is a steel possessing specific material properties of ductility, and strength desired for the housing assembly 10.

[0030] The subsequent stamping operations performed indicated at 54 and 55 are conducted to provide the final configuration of the upper and lower housings 12, 14. The stamping operation 54 forming the upper housing 12 includes formation of the opening 22. The stamping operation 55 forming the lower housing 14 includes formation of the bowl portion 24.

[0031] The upper and lower housings 12, 14 are then joined as indicated at 56 byaweld along the seam 46. The base structure of the housing assembly 10 is complete after the upper and lower housings 12, 14 are joined because the lower housing 14 includes the unified bowl portion 24. The chamber 48 formed between the upper and lower housings 12, 14 is complete upon completion of the joining operations 56.

[0032] Final assembly is indicated at 58 and includes installation of the differential gear assembly 42, along with the wheel mount assemblies 40 at first and second ends 38, 39 of the housing assembly 10. The unified formation of the bowl portion 24 with the lower housing 14 encloses the gear 44 of the gear assembly 42 concurrently with assembly into the opening 22 of the upper housing 12.

[0033] The unified structure of the lower housing 14 reduces cost and assembly operations required for fabrication of the axle housing assembly 10. Further, the unified structure of the lower housing 14 eliminates the number of parts and the number of joint forming the housing assembly 10. The elimination of additional parts and joints reduces potential leakage points for lubricant contained within the chamber 48. In addition, the unified bowl portion 24 increases the structural rigidity of the overall axle housing assembly 10 to improving function and durability properties.

[0034] The foregoing description is exemplary and not just a material specification. The invention has been described in an illustrative manner, and should be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications are within the scope of this invention. It is understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention. 

What is claimed is:
 1. A method of fabricating an axle housing assembly, said method comprising the steps of: a) plastically deforming a first sheet of material to form an upper housing, said upper housing including first and second upper leg portions extending from a mount section; b) plastically deforming a second sheet of material to form a lower housing, said lower housing including first and second lower leg portions extending from a bowl portion, said bowl portion extending outwardly from said lower leg portions; and c) joining said upper housing to said lower housing.
 2. The method of claim 1, wherein step a) comprises forming a gear assembly chamber between said upper and lower housings and an opening to said gear assembly chamber within said upper mount section.
 3. The method of claim 2, wherein step c) comprises joining said bowl portion opposite said opening.
 4. The method of claim 3, wherein step b) comprises forming a longitudinal surface as part of said lower housing and extending said bowl portion outwardly beyond said longitudinal surface.
 5. The method of claim 4, including the step of installing a gear assembly having a gear into said gear assembly chamber.
 6. The method of claim 5, comprising the step of enclosing said gear within said upper and lower housings while installing said gear assembly.
 7. The method of claim 6, further defined as extending a portion of said gear assembly past said longitudinal surface.
 8. The method of claim 1, wherein said step b) comprises forming said first and second lower leg portions and said bowl portion as a single unified structure.
 9. The method of claim 8, wherein said step c) comprises joining said upper and lower leg portions to form openings at a first and second end of said upper and lower leg portions.
 10. The method of claim 9, including the step of assembling wheel mount assemblies to each of said first and second ends of said upper and lower leg portions.
 11. The method of claim 1, wherein said step c) comprises welding along a seam between said upper and lower housings.
 12. The method of claim 1, wherein steps a) and b) comprise a stamping operation.
 13. An axle housing assembly comprising: an upper housing formed from a first sheet of material, said upper housing having upper leg portions extending from a mounting section, said mounting section having an opening; and a lower housing including first and second lower leg portions extending from opposite sides of a bowl portion, said lower housing joined to said upper housing and formed from a second sheet of material, said lower housing having a continuous wall extending from said first lower leg portion through said bowl portion to said second lower leg portion.
 14. The assembly of claim 13 including a differential gear assembly mounted to said upper housing, said differential gear assembly including a gear extending through said opening and into said bowl portion.
 15. The assembly of claim 14, wherein said lower housing includes a surface defining a plane and said bowl portion extends outward within said lower housing past said plane.
 16. The assembly of claim 15, including a chamber defined within said upper and lower housings into which said gear extends, said bowl portion extending said chamber beyond said plane such that said gear portion is enclosed within said upper and lower housings.
 17. The assembly of claim 13, wherein s aid first and second lower leg portions and said bowl portion are a single unified structure. 